For all iSonics: Take the tail width (width one foot off (30,5cm)) and the longest fin is -4cm the shortest -8cm.
E.G. tail widht iS101 09 = 45,4cm: max is a 41/42cm fin and min a 37/38
use the shortes for small sails and the longest for your biggest sail :-)
For top speed purposes and deep downwind you can go down to -10cm but not more. Better to use than a smaller board.

4th December 2008 08:08 PM

Unregistered

Used google: search::: "isonic 105 site:gps-speedsurfing.com"

My last SB was a Is105... Did 1,5 yrs ago 72kmh almost 40kn topspeed on it. But recorded by Garmin Foretrex 201 (not really reliable).

Thanks for the advice.
I was only going to buy the select sl07 37cm for my 7,3 sail but there was a 50% discount on maui fins sl from 2007 so i figured i could extend the board high wind range with a smaller fin for use with 5,8 sail unfortunately there was no 30cm fin and i tought that 32cm was a bit to close to the 34 that i have(looking back the 32 would have been the best choice). I was not fully aware that wider boards require bigger fins. Because I only have one slalom board I have to try and make it work in as wide range as possible. If we get 30knots of wind I will give it a try and if it does not work I can keep it untill I get a smaller board. I will try to get back with my impression, might be a while untill I get the conditions for it tough.

3rd December 2008 08:34 AM

Rave On

New Hawaii State Record!

On Monday 11-24-08 Pieter Bijl set the new 100m record for Hawaii at 41.4 knots. Pieter was sailing at Kanaha on a Fanatic Falcon with a 28cm Vector fin and a Neil Pryde prototype sail. The winds were gusting over 35 knots.

3rd December 2008 07:04 AM

Unregistered

Some people can go very fast with small fins, I did my highest speeds with an 30cm tectonics falcon f1 on a Is105. If you are not the power style surfer you could use this fin. This fin gives somhow a lot of acceleration @ 110-120 degrees downwind

If you like power on the fin I would go for the Select sl7 33cm, this fin is really fast deeeeeep downwind.

2 different styles, both very fast. 30cm doesn't work in no-wind, 33cm is easier to control. >33cm fins will be harder to ride on tight courses in strong winds. Only very experienced/ strong/heavy surfers can handle that.

Lots of deboichet fans around here, sorry I am no deboichet fan since I am confinced that select & tectonics deliver at least the same performance. Albeau used tectonics falcon f1 on fuerte/karphatos speed world cup (on videos & pics...)

Back on-topic ====> 28cm sounds to small... Don't go smaller!!!

2nd December 2008 03:24 PM

Chris Pressler

Hi Per Oxid,
I would not go shorter than 34 with the 7,3. The 101 is wide in the tail and needs a long sized fin. For Slalom sizes from 36 to 42 fit. My favourite is a 38.
But find it out and measure your speed. Would be interesting, if a shorter fin would work great. I can remember a competition on the Philippines: it was a lagoon spot and the organiser decided to run a speed event. I only had the iSonic 125 with me and the tide was low. I had to take a very short fin. It was a real compromise. First I took a 34, imagine. This one broke crashing something on the ground. I just had a 32 in the bag, because I knew from other Asian spots, that it can be shallow (Koh Samui in Thailand). Fully powerde up with a 7,6 on the wide board I had the chance to attend the competition. The speed was ok.

Chris

2nd December 2008 02:47 PM

Per_oxid

Thanks alot that helps. I bought a select sl7 37 but could not resist the small 28 that was at halfprice, guess i can keep it untill i get a smaller speed board. I could perhaps use the included drake 34 as a speed fin then.

2nd December 2008 04:11 AM

Remi

Hi Per,

I use SL3 or SL4 28 on the W49 speed secial, so this size is way too small for the iSonic 101. My smaller fin on it is SL4 34, but for speed in really flat water 32 may be works.

Also the best size sails for this board turn around 6,7.

Hope this help.

All the best

1st December 2008 10:28 PM

Per_oxid

Recomended smallest fin for IS101 and speed sailing

I only have one slalom board the IS101 and it has ben working well. I have not taken it out in very windy conditions yet but i got it to33knots quite easy with a 7,3. I think I can make it go faster in more wind and a smaller sail but is uncertain on how small a fin I should use. I just bought a Maui fin sl28 for really windy days and smaller sails 5,2-5,8m2, my other fins are 34 37 and 42. The question is how small sail is comfortable using on this big board and how small fin can you go for, should the 28 be fine as a smallest fin or is it to small even for speed on windy days.
Regards
Per